1. Field of the Invention
The present invention relates to a sealing device with a magnetic encoder capable of sensing a rotation rate, rotational speed, rotational angle or the like of a rotating shaft. The sealing device according to the present invention may be mounted, for example, on an engine block of vehicles such as automobiles, so as to be slidingly contacted on an outer periphery of a crank shaft for sealing of sealed fluid such as engine oil and the like.
2. Description of the Conventional Art
A conventional sealing device 51 with an encoder as shown in FIG. 7 is known, and this sealing device 51 has an oil seal 54 mounted on an inner periphery of a shaft hole of a housing 52 and slidably contacted on an outer periphery of a rotating shaft 53, and a magnetic encoder 55 mounted on the rotating shaft 53 to be rotated therewith.
However, in the above-mentioned conventional sealing device 51, there is an disadvantage that relatively large installation space or width is needed in an axial direction, since a metal ring 56 of the oil seal 54 and the magnetic encoder 55 are arranged in series in an axial direction, i.e. the metal ring 56 and the magnetic encoder 55 are not arranged in an overlapped-relation with each other.
This is due to the fact that the magnetic encoder 55 is merely added to the conventional sealing device 51 in general having only the oil seal 54 as a constituent component. Since a space for installing the sealing device is limited, it is desirable that the installation width of the entire sealing device 51 in the axial direction is made as small as possible.
Further, although a seal lip 57 of the oil seal 54 is formed with a polymer material such as PTFE, and engine oil, which is fluid to be sealed, exists in an interior side A of the housing, the seal lip 57 is disposed towards an exterior side B of the housing. Therefore, the leak-out probability of the engine oil inside the housing is high, and when the engine oil leaks out and disperses, the engine oil may adhere to the magnetic encoder 55, causing detrimental effects on the magnetic function thereof.
For the conventional sealing device, refer to, for example, JP-2004-093554 A.